1. Field of the Invention
This invention relates to the preparation of composite structural materials in general and to the formation of composites from extensible resin systems with fiber reinforcements in particular.
2. Prior Art
Fiber reinforced composite systems are well known as structural materials. The closest facsimiles to the present invention known are the chopped commercial fiber-filled systems. However, such fiber incorporations into curable resins yield composites which exhibit mechanical properties totally different from that of composites prepared by the present invention. While prior art fiber filled composites exhibit high moduli, a decrease in percent elongation and strength often results. The behavior of the prior art fiber-filled composites under repeated loading also appears to be totally different from that of composites prepared by the instant invention.
In U.S. application Ser. No. 616,747, Applicant Keller and another disclosed a process for forming polymeric fibers "in situ". This disclosure teaches that fibers formed "in situ" exhibit a randomly oriented three-dimensional interconnected structural network. However, these fibers were formed in a polymerizable medium or were secondarily impregnated with a polymerizable medium which, when subsequently cured formed a rigid matrix with very little capability to elongate under stress. The composites so formed were strong with very low capabilities to strain or deform under load.
While composites prepared by the teachings as disclosed in U.S. application Ser. No. 616,747 have useful applications, they are not useful in applications requiring high flexibility, a lack of deterioration in mechanical properties on repeated loading, as well as high strength composites. Applicants herein sought to extend the teachings of the Ser. No. 616,747 application to yield composites which fulfill the requirements of the latter type of applications.